The prior art includes telephone circuit testing equipment for measuring the percent break of DC dialing equipment. When a telephone is dialed the circuit is broken a number of times corresponding to the number being dialed. The length of the break divided by the total time between the start of subsequent breaks is defined as the percent break. It is important that this ratio be maintained within predetermined limits to insure proper operation of the switching relays in the telephone circuits. Accordingly, the industry has developed testing equipment which measures the duration of these breaks in the DC current to provide an indication of this ratio.
With the advent of modern telephone signaling systems it has become common to use each of the breaks in the dial sequence to generate an AC tone burst of duration equal to that of the break. The tone bursts are easier to transmit over long distances and more easily identifiable to the switching equipment. However, after a tone burst passes through the various filters, transformers, and other electronic telephone circuits, its shape is modified so that it is difficult to positively identify the start and the end of the pulse. Thus, it is difficult to measure the length of the tone burst pulse and determine the percent break. My invention overcomes this problem as described hereinafter.